Organs consist of multiple cell types and multiple tissue types. For the last 70 years, increasingly specialized media have been developed for individual cells and tissue types. Media development has historically focused on developing formulations where the product is designed to grow cancerous cells as rapidly as possible. Much of the focus has been on supplying nutrients, regulating pH, and using frequent media changes to remove wastes.
Nature has devised a universal “medium,” blood, which arguably can sustain a plethora of phenotypically and functionally distinct cell types. While blood can perform a plethora of functions in an animal or human, whole blood unfortunately becomes rapidly toxic in cell culture due to agglutination on account of cross-reactive white blood cells, and hemolysis from the short lifespan of red blood cells. So far, no available media formulation can perform all of the tasks that blood can perform.